The overall goal of the proposed study is to investigate those differences which exist between normal, preneoplastic and neoplastic mouse mammary epithelial cells in monolayer and suspension cultures as a model system for the study of similarly cultured human tissues. Our immediate objective, however, is to establish rapid and sensitive assay procedures to distinguish these cells from each other based upon alteration in growth and differentiation which occurs as a result of changing cell culture conditions. New techniques make it possible to obtain and cultivate human mammary epithelial cells from samples of human milk. The use of the cell culture technique for diagnosis is now possible. These efforts, however, are hampered by our inadequate ability to recognize preneoplastic and neoplastic cells in culture. Simple histochemical localization of lactational products characteristic of normal mammary epithelial cells is not sufficient for identification purposes, since preneoplastic and neoplastic mammary tissues also synthesize milk products. An alternative must be found. The ability of normal mammary cells to synthesize products found in milk is regulated, both in vivo and in vitro, by a variety of nutritional, hormonal and cell-associated growth factors. On the other hand, cells from tumors and preneoplastic tissues possess altered abilities to respond to these various agents. Therefore the objectives of this study are (1) to analyze the responsiveness of normal virgin, pregnant and lactating mammary epithelial cells to these varying conditions, (2) to compare the normal responses to those of preneoplastic and neoplastic cells, and (3) to establish rapid and sensitive assay procedures to characterize cells under various cell culture conditions. As these objectives are achieved, information gained will be readily applied to human mammary epithelial cell cultures. BIBLIOGRAPHIC REFERENCES: Foster, R. C. and M. K. Feldman (1975). Technique for Mammary Epithelial Cell Isolation and Cultivation. In: Tissue Culture Association Manual: Techniques, Methods, and Procedures for Cell, Tissue and Organ Culture, V. J. Evans, P. Perry and M. M. Vincent (eds.), ppl 27-30. Feldman, M. K, and d. Wong (1976). Effect of Various Sera on Plating Efficiency and Thymidine Incorporation in Murine Mammary Epithelial Cells, American Zoologist, in press.